How steep can a concrete ramp be and still meet the accessibility rules? The US Access Board’s 2010 ADA Standards answer with a ratio, 1:12, and a short list of limits that go with it. This guide gives each limit with its section number, then works the arithmetic for a real rise.
Under the 2010 ADA Standards, a ramp run on an accessible route has a running slope no steeper than 1:12 (section 405.2). That is 1 inch of rise per 12 inches of run, about 8.33 percent (arithmetic). One run may rise 30 inches at most (405.6). Home ramps may fall under other local rules.
What Is the Maximum Slope for an Accessible Concrete Ramp?
Section 405.2 of the 2010 ADA Standards says ramp runs must have a running slope not steeper than 1:12. Every limit in this guide is for ramps on accessible routes under those Standards (section 405.1), as published by the US Access Board.
A 1:12 slope means 1 inch of rise for every 12 inches of run. As a percentage that is about 8.33 percent (arithmetic: 1 / 12 = 0.0833). Section 405.3 adds a separate limit: cross slope on a ramp run may not be steeper than 1:48. Per foot, 1:48 is 1/4 inch (arithmetic: 12 / 48 = 0.25).
Section 405.4 says changes in level other than the running slope and the cross slope are not permitted on ramp runs. The drawing below compares a 1:12 run with a 1:6 run that has the same rise.
How Long Does a Ramp Need to Be for Your Rise?
At the 1:12 limit, each inch of rise needs 12 inches of run. This is arithmetic from the ratio, not a separate rule in the Standards.
Section 405.6 limits the rise of any ramp run to 30 inches. Thirty inches times 12 is 360 inches, which is 30 feet (arithmetic: 360 / 12 = 30). So the longest single run at 1:12 and the maximum rise is 30 feet.
A 24 inch rise needs 24 x 12 = 288 inches of run, or 24 feet (arithmetic). The Access Board Guide says there is no limit on the number of runs a ramp may have, and section 405.7 puts landings between runs. To turn a run, rise and width into cubic yards, use the concrete ramp calculator.
Which Width, Landing and Handrail Limits Apply?
Section 405 sets width, landing and handrail limits beside the slope limits. The table lists each one with its section number, as the 2010 Standards state them for ramps on accessible routes.
| Item | Limit | Section |
|---|---|---|
| Running slope | Not steeper than 1:12 | 405.2 |
| Cross slope | Not steeper than 1:48 | 405.3 |
| Changes in level | None other than the two slopes | 405.4 |
| Clear width | 36 in minimum, between handrails where provided | 405.5 |
| Rise per run | 30 in maximum | 405.6 |
| Landings | At the top and bottom of each run | 405.7 |
| Landing clear width | At least as wide as the widest run leading to it | 405.7.2 |
| Landing clear length | 60 in minimum | 405.7.3 |
| Landing where the ramp changes direction | 60 in by 60 in clear minimum | 405.7.4 |
| Handrails | Required where a run rises more than 6 in | 405.8 |
| Edge protection | Surface extends 12 in past the handrail, or a curb or barrier stops a 4 in sphere | 405.9 |
Some sections list exceptions that the table leaves out, so read the section text before you rely on a row. Section 405.7.1 sends landings to section 302 and says changes in level are not permitted on them, with a 1:48 slope allowed. The handrail design rules in section 505 were not read for this guide.
What Do the Standards Say About Edges, Surfaces and Concrete?
Section 405.9 requires edge protection on each side of ramp runs and landings, and the Standards give two ways to meet it. One is a surface that extends 12 inches past the inside face of the handrail (405.9.1). The other is a curb or barrier that stops a 4 inch sphere (405.9.2).
The Access Board Guide adds that curbs, if used for edge protection, must be at least 4 inches high. Section 302.1 requires floor and ground surfaces to be stable, firm and slip resistant, and landings are sent to that section.
The Guide also covers concrete directly. It says the running slope is to be uniform along a run, "although slight variations may occur with certain materials such as concrete". The Guide then adds a recommendation, not a requirement: a running slope of 7.5 percent maximum and a cross slope of 1.5 percent maximum for exterior ramps, which it says will accommodate most irregularities from construction methods or materials, according to a study sponsored by the Access Board. Both figures sit below the 1:12 (8.33 percent) and 1:48 limits.
Ramps often sit beside walks and steps. For those, see how wide a walkway should be, which covers walkway width and cross slope, and concrete step dimensions.
Do the ADA Standards Cover a Home Ramp?
The Standards apply to the facilities the ADA covers, and the wording on private residences comes from the regulations on ADA.gov. Under 28 CFR 36.401(b), for a commercial facility located in a private residence, the portion of the residence "used exclusively as a residence" is not covered by that subpart.
Section 36.406(b) says the Standards apply to fixed or built-in elements of buildings, structures, site improvements and routes on a site. The ADA.gov page has the full text of both sections.
State and local building codes, and the International Residential Code, may still set rules for a home ramp. Those codes were not read for this guide, so it gives no residential slope and no IRC section number. Check your local code with your building department.
The same holds for driveway aprons, loading ramps and other ramps that are not on an accessible route. The sources read give no rule for them.
Existing Buildings and Table 405.2
Table 405.2 allows steeper slopes only in existing sites, buildings and facilities, and only where space limitations make it necessary. A slope steeper than 1:12 up to 1:10 is allowed for a rise of 6 inches maximum. A slope steeper than 1:10 up to 1:8 is allowed for a rise of 3 inches maximum. Steeper than 1:8 is prohibited. Section 405.2 points to this table as an exception for existing construction only.
What Does the Ramp Calculator Check About Slope?
The ramp calculator sizes concrete for a ramp you describe, and it checks no slope rule. Its default is a 12 foot run, a 24 inch rise and a 4 foot width, which is a 1:6 slope. These steps are arithmetic, with no landing and 10 percent waste.
- Default volume. The rise is 24 / 12 = 2 ft. A ramp wedge is half a box: (12 x 2 x 4) / 2 = 48 cu ft.
- Add waste. 48 x 1.10 = 52.8 cu ft.
- Convert to yards. 52.8 / 27 = 1.96 cu yd, the figure the calculator shows for these inputs.
- Find the grade. 2 ft / 12 ft = 1/6, which is 16.7 percent and a 1:6 slope. That is steeper than the 1:12 limit in section 405.2.
- Redo it at 1:12. For the same 24 inch rise, the run is 24 x 12 = 288 in = 24 ft. Volume is (24 x 2 x 4) / 2 = 96 cu ft. Then 96 x 1.10 = 105.6 cu ft, and 105.6 / 27 = 3.91 cu yd.
The 3.91 cu yd figure is arithmetic for a 1:12 run with no landings. It is exactly twice the 52.8 cu ft of the default, because the run doubles and the width stays at 4 feet. The calculator also has a landing field, which this example leaves at zero.
Enter your own run, rise and width to size your ramp’s concrete, then compare the grade it shows with the limits above. For related flat work, see the slabs and flatwork calculators.
FAQs About Concrete Ramp Slope
How steep can an accessible ramp be?
Section 405.2 of the 2010 ADA Standards limits a ramp run on an accessible route to a slope no steeper than 1:12. That is 1 inch of rise per 12 inches of run, about 8.33 percent (arithmetic).
How long must a ramp be for a 24 inch rise?
At 1:12 the run is 24 x 12 = 288 inches, or 24 feet (arithmetic). Section 405.2 allows a steeper run only in existing buildings under Table 405.2.
What is the maximum rise before a landing is needed?
A single run may rise 30 inches at most (405.6). Landings are required at the top and bottom of each run (405.7), and the Access Board Guide says the number of runs is not limited.
How wide must an accessible ramp be?
Section 405.5 sets a clear width of 36 inches minimum for a ramp run, measured between handrails where handrails are provided. Landings must be at least as wide as the widest run (405.7.2).
When are handrails required on a ramp?
Section 405.8 requires handrails on ramp runs with a rise greater than 6 inches. The handrail design rules in section 505 were not read for this guide, so check that section for details.
Do the ADA Standards apply to a home ramp?
ADA.gov’s 28 CFR 36.401(b) says the part of a residence used exclusively as a residence is not covered by that subpart. State and local codes may still apply and were not read, so check your local code.
Can an existing building use a steeper ramp?
Table 405.2 allows it only in existing buildings and sites where space limits require it: up to 1:10 for a rise of 6 inches, and up to 1:8 for 3 inches. Steeper than 1:8 is prohibited.
Sources and Further Reading
References Used in This Article
- US Access Board, 2010 ADA Standards for Accessible Design, accessed 2026-10-21.
- US Access Board, Guide to the ADA Accessibility Standards, Ramps and Curb Ramps, accessed 2026-10-21.
- ADA.gov, Title III Regulations (28 CFR Part 36), accessed 2026-10-21.
This guide summarizes ramp limits from the 2010 ADA Standards and is not an engineering design. The ADA Standards set a 1:12 limit for ramps on accessible routes, so confirm the rule that applies to your ramp with your local building department. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated 2026-10-21.
Shakeel Muzaffar is the Founder and Editor-in-Chief, with over 15 years of experience in digital publishing and online tool development. He oversees editorial quality and formula verification to ensure accurate, practical, and easy-to-use calculators.